Nisin
Nisin is a polycyclic peptide antibacterial with 34 amino acid residues used as a food preservative. It contains the uncommon amino acids lanthionine (Lan), methyllanthionine (MeLan), didehydroalanine (Dha) and didehydroaminobutyric acid (Dhb). These unusual amino acids are introduced by posttranslational modification of the precursor peptide. In these reactions a ribosomally synthesized 57-mer is converted to the final peptide. The unsaturated amino acids originate from serine and threonine, and the enzyme-catalysed addition of cysteine residues to the didehydro amino acids result in the multiple thioether bridges.
Nisin is produced by fermentation using the bacterium Lactococcus lactis. Commercially it is obtained from natural substrates including milk and is not chemically synthesized. It is used in processed cheese production to extend shelf life by suppressing gram-positive spoilage and pathogenic bacteria. There are many other applications of this preservative in food and beverage production. Due to its highly selective spectrum of activity it is also employed as a selective agent in microbiological media for the isolation of gram-negative bacteria, yeast and moulds. Subtilin and Epidermin are related to Nisin, all members of a class of molecules called lantibiotics.
As a food additive, nisin has E number E234.
Further reading
- K. Fukase et al., Tetrahedron Lett. 1988, 29, 7, 795. (Total synthesis)
- G. W. Buchman et al., J. Biol. Chem. 1988, 263, 31, 16260. (Biosynthesis)